In reluctance motors it is common to provide stator poles which are cooperating in pairs and which are equally disposed along the way of movement of the rotor poles. Like the stator, the rotor has a shape such that its poles are cooperating in pairs. Hence, during the turning of the rotor, the two poles of a stator pole pair simultaneously cooperate with the corresponding poles of a rotor pole pair. In operation, the stator pole pairs are connected to a source of DC voltage in proper order and, in principle, a selected stator pole pair is connected to the DC voltage upon a rotor pole being about to turn over the stator pole. The voltage remains until the rotor pole has been fully turned over the stator pole. For the control of the motor speed the moments of connecting and disconnecting, respectively, of the supply voltage can be varied.
Detailed information about reluctance motors of the kind indicated has been published under the heading "Variable-speed Switched Reluctance Motors" in IEE PROC., Vol. 127, Pt. B, No. 4, July 1980.
The moments of connection and disconnection of the stator pole pairs are controlled by sensors indicating those positions in which a rotor pole begins to overlap a stator pole. In order for the rotor at start to turn in the desired direction, up to now one sensor has been required for each stator pole pair.